A 79-year-old grandmother from Warr Acres was arrested Tuesday morning after using a bicycle lock to attach herself to an excavator being used to build the southern segment of the Keystone XL pipeline.

Nancy Zorn was jailed in Hughes County when she refused to leave developer TransCanada Corp.'s right of way on the pipeline route near Allen.

She is concerned about the potential environmental impact of a spill since the pipeline will be carrying diluted bitumen from Canada's oil sands.

“I can no longer sit by idly while toxic tar sands are pumped down from Canada and into our communities,” Zorn said in a statement issued by the Great Plains Tar Sands Resistance. “It is time to rise up and defend our home.

“It is my hope that this one small action today will inspire many to protect this land and our water.”

Zorn is at least the third person arrested in Oklahoma for trying to block construction of the pipeline. Seven others also are facing trespassing charges in Seminole County after a Feb. 11 protest near Schoolton.

Keystone spokesman Jim Prescott said the protests have not interfered with construction of the 485-mile line meant to link the oil storage hub at Cushing with refineries in the Houston area.

The pipeline is expected to be completed by the middle of this year, with plans to have it in service by the end of 2013.

TransCanada opted to build Keystone XL's southern leg after the Obama administration refused to grant a permit for the full transcontinental pipeline last year.

The company has reapplied for a permit after changing the pipeline's route through sensitive wetlands in Nebraska.